Blade Sharpener

ABSTRACT

A blade sharpener including a frame casing body having a grip and a grinding chamber and a grinder assembly detachably installed in the grinding chamber in which the grinder assembly is formed by a grinder casing body having a pair of vertical walls facing each other, a supporting window provided in each of the vertical walls, a rotary shaft provided between the vertical end walls with both end thereof in the supporting windows of the vertical walls, an abrasive wheel provided on the rotary shaft at the axial center, and a pair of lateral coil springs each provided on either side of the abrasive wheel. The rotary shaft can be supported by a pair of longitudinal coil springs installed in the vertical walls.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a blade sharpener that sharpens blades such as kitchen knives and table knives with an abrasive wheel and more particularly to a manual blade sharpener having an abrasive wheel therein.

2. Background Art

Japanese Patent Application Laid-Open (Kokai) No. S62-181860 discloses a table knife sharpener that is comprised of a frame casing body, a adhesive wheel rotatably installed in this frame casing body and equipped with grinding surfaces that are of a truncated cone shape and forming an angle to each other, a guide part that guides the blade so that the blade being sharpened is pressed against both grinding surfaces, and a liquid vessel installed in the frame casing body so as to surround the bottom part of the abrasive wheel.

In this device, two sides of the blade of a knife is pressed against the two sides of the grindstone and the knife is moved back and forth at a bias relative to the axial direction of the abrasive wheel that has truncated conical grinding surfaces to sharpen both sides of the blade. This device has problems, however. During sharpening by the back and forth movements of the blade, frictional heat is generated, thus dulling the blade. Grinding dust from the blade would clog the pores of the abrasive wheel. Though the liquid vessel that contains liquid for cooling and cleaning the blade during the sharpening is provided, the problems of the frictional heat and clogging are not sufficiently solved. Furthermore, since the abrasive wheel is fixedly provided in the frame casing body, it is difficult to wash and clean the abrasive wheel.

Japanese Utility Model Registration No 3007312 discloses a blade sharpener that is to solve the problems above. This blade sharpener includes a frame casing body having a grip and a grinding chamber, a rotary shaft rotatably installed across the grinding chamber and arranged at a bias to the direction of the length of the frame casing body, an abrasive wheel that is installed in the center of the rotary shaft and has grinding surfaces which are truncated cones and form an angle to each other, a guide part that guides the blade so that the blade being sharpened is pressed against the two grinding surfaces, and a liquid vessel installed in the grinding chamber so that the liquid therein for cooling the abrasive wheel can surround the bottom part of the abrasive wheel. Also, Japanese Utility Model Registration No 3010973 discloses a sharpener for a single-blade knife in which a grinding element is comprised of a pair of roller bodies having conical surfaces and one of the conical surfaces is a grinding surface and the other conical surface is a smooth, hard, non-grinding surface.

In these blade sharpeners described above, the side of a blade is, while being pressed against the grinding surface, sharpened by moving the blade back and forth along the guide part while it is being pressed against the conical surface of an abrasive wheel. Accordingly, sharpened conditions of blades can differ depending on how (in terms of pressing loads, pressing angles, etc.) the blade is pressed against the abrasive wheel. Pressing the blade too firmly will create defects in the cutting edge and can leave it to be able to cut less than before. In addition, blades with serrated cutting edges and fine ceramic blades cannot be sharpened very well even with use of a diamond abrasive wheel for the grinding surface.

Japanese Utility Model Registration No 3128435 discloses a blade sharpener that is to overcome the problems described above, and in this sharpener a rotary shaft that has a abrasive wheel is supported at both end thereof by a pair of vertically installed springs so that the blade can be evenly pressed against the abrasive wheel and evenly grinded by the conical surfaces of the abrasive wheel.

SUMMARY OF THE INVENTION

Accordingly, the present invention is made with the above problems in mind, and it is an object of the present invention to provide a blade sharpener that is able to prevent variations in the force of pressing the cutting edge against conical surfaces of an abrasive wheel and can grind blades further evenly and smoothly compared to the existing blades sharpeners such as those described above.

The above object is accomplished by a unique structure of the present invention for a blade sharpener that comprises:

-   -   a frame casing body having a grip and a grinding chamber; and     -   a grinder assembly which is detachably installed in the grinding         chamber and comprised of:         -   an empty substantially rectangular block shape grinder             casing body having a pair of vertical walls facing each             other,         -   a supporting window provided in each of the vertical walls,         -   a rotary shaft provided between the vertical walls with both             end thereof in the supporting windows of the vertical walls,         -   a grinding element provided on the rotary shaft at             substantially an axial center thereof, and         -   a pair of horizontally urging means each provided on either             side of the grinding element.

Furthermore, the above objects are accomplished by another unique structure of the present invention for a blade sharpener that comprises:

-   -   a frame casing body having a grip and a grinding chamber; and     -   a grinder assembly which is detachably installed in the grinding         chamber and comprised of:         -   an empty substantially rectangular block shape grinder             casing body having a pair of vertical walls facing each             other,         -   a supporting window provided in each of the vertical walls,         -   a vertically urging means provided in each of the vertical             walls,         -   a rotary shaft provided between the vertical walls with both             end thereof in the supporting windows of the vertical walls             and on the vertically urging means,         -   a grinding element provided on the rotary shaft at             substantially an axial center thereof, and         -   a pair of horizontally urging means each provided on either             side of the grinding element.

In the structures of the present invention as describe above, since the grinding element of the blade sharpener is constantly urged by the two lateral urging means or coil springs so that the grinding element is at the middle of the distance between the two vertical walls during the grinding process, the blade being grinded receives lateral pressure (or pressing force) from both sides by the urging means and makes good contact with the grinding element when the blade is moved back and forth with respect to the grinding element and as a result is sharpened smoothly and efficiently. Furthermore, in the structure that further, includes the vertical coil springs, the blade that is receiving downward pressing force against the grinding element by the user further receives upward pressing force caused by the vertical coil springs that is in the direction opposite from the downward pressing force, in addition to the lateral pressure by the lateral urging means (or coil springs). Accordingly, the blade receives not only the lateral pressure but also the longitudinal pressure (or pressing force) from four directions and thus can make further good contact with the grinding element when the blade is moved back and forth with respect to the grinding element, and the blade is thus sharpened further smoothly and efficiently.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a front view of a frame casing body of the blade sharpener according to the present invention;

FIG. 2 is a top view thereof with the cover casing of the frame casing body removed;

FIG. 3A is an enlarged side view of holding means and FIG. 3B is an enlarged top plan view thereof;

FIG. 4A is a vertically cross-sectional view of first type of grinder assembly according to the present invention with a symmetric abrasive wheel employed, and FIG. 4B is a side view thereof;

FIG. 5 illustrates an arrangement of grinder assemblies installed in the grinding chamber of the blade sharpener of the present invention;

FIG. 6 is a vertically cross-sectional view of the first type of grinder assembly according to the present invention with an asymmetric abrasive wheel is employed;

FIG. 7 illustrates the grinder assembly of FIG. 4A with the abrasive wheel depressed down during grinding;

FIG. 8A is a vertically cross-sectional view of another type of grinder assembly according to the present invention with a symmetric abrasive wheel employed, and FIG. 8B is a side view thereof;

FIG. 9 is a vertically cross-sectional view of the other type of grinder assembly according to the present invention with an asymmetric abrasive wheel is employed;

FIG. 10 is a top view of a frame casing body of a blade sharpener in which the cover casing is formed with one single blade slit so that a single grinder assembly is installed in the grinding chamber;

FIG. 11 illustrates the cross-section of a known double-edged blade; and

FIG. 12 illustrates the cross-section of a known single-edged blade.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of a blade sharpener according to the present invention will be described in detail below with reference to the accompanying drawings.

FIGS. 1 and 2 illustrate an example of a frame casing body 1 of the blade sharpener according to the present invention. The frame casing body 1 is made of, for instance, synthetic resin and includes a grip 2 and a grinding chamber 3 which is connected to the end of the grip 2 and is substantially in a rectangular box shape having a size of for instance 2.5 inches (W)×4 inches (L)×2.5 inches (H). The grinding chamber 3 is provided with a removable cover, casing 4 covering the upper opening of the grinding chamber 3, and this removable cover casing 4 is formed with two blade guide slits 5 which extend in the width direction W of the grinding chamber 3 so as to open continuously to the above and to both sides of the cover casing 4.

On the rectangular bottom 3 a of the grinding chamber 3, one pair of (or two) holding means 6 are provided. As seen from FIGS. 3A and 3B, each one of the holding means 6 is comprised of four projections 6 a each of which is in a shape of L when viewed from above (or through the removable cover casing 4). Four projections 6 a form a rectangular shape (when they are connected with dotted lines, see FIG. 3B) that is substantially the same as (or slightly smaller than) the bottom of each one of grinder assemblies 10 (described below), so that the grinder assembly 10 is held by the four projections 6 a when the grinder assembly 10 (or the bottom thereof) is pressed (by hand of a user of the sharpener) against the rectangular area defined by the four projections 6 a from above so that the four corners of the grinder assembly 10 are respectively in contact with the four projections 6 a that are each in an L shape when viewed from above as described above. Since the holding means 6 (or the four projections 6 a ) and the grinder assembly 10 are made of resins or plastics, and the bottom of the grinder assembly 10 is slightly larger than the area defined by the four projections 6 a, the grinder assembly 10 can be secured tightly in position by the holding means 6 and nonetheless can be separated therefrom when the grinder assembly 10 is forcedly lifted (by hand). The grinder assembly 10 is thus removed from the grinding chamber 3 for, for instance, cleaning of the grinder assembly 10 (and the grinding chamber 3) and for replacement thereof.

Each one of the pair of grinder assemblies 10 that are detachably installed in the grinding chamber 3 of the frame casing body 1 as described above (they can thus be called grinder cassettes in view of the removability) comprises as shown in FIGS. 4A and 4B a grinder casing body 10A formed by a rectangular bottom plate 12, a pair of end walls 14 vertically formed along the two shorter side edges of the rectangular bottom plate 12 so as to face each other, and a pair of side walls 16 formed along two longer side edges of the rectangular bottom plate 12 to face each other (The side walls 16 are lower than the end walls 14 so as to allow a blade, an abrasive wheel and a rotary shaft to be moved down as described below). Thus, the frame casing body 1 in this example is an empty substantially rectangular block shape. In each one of the pair of (or two) vertical end walls 14 facing each other, a supporting window 14A is opened, and below this supporting window 14A, a vertical channel 14B is provided. In this vertical channel 14B, a longitudinal coil spring 20, which is greater (longer) than the depth of the vertical channel 14B, is installed so as to stand vertically within the vertical channel 14B. Thus, an upper end portion of the longitudinal coil spring 20 is outside of the vertical channel 14B to project out therefrom and is located inside the supporting window 14A. A supporting piece 20A is attached to the top end of the longitudinal coil spring 20 so that it is in the supporting window 14A.

The grinder casing body 10A thus having a pair of longitudinal coil springs 20 further includes a rotatable shaft 22. This rotatable shaft 22 is provided inside the grinder casing body 10A horizontally with its both ends inside the supporting windows 14A of the end walls 14 and on the supporting pieces 20A of the coil springs 20. To the top surface of each one of the end walls 14 of the grinder casing body 10A is attached a holding piece 14C so as to cover the upper opening of each of the windows 14A and prevent the rotatable shaft 22 from being removed upwardly from the supporting windows 14A (or from the end walls 14 of the grinder assembly 10). The diameter of the rotatable shaft 22 is (slightly) smaller than the width W′ of the supporting window 14A, and the height H′ of the supporting window 14A is greater than the width W′ of the supporting window 14A for the substantially the same amount (length) as the upper end portion of the longitudinal coil spring 20 projecting out of the vertical channel 14B into the supporting window 14A. As a result, the rotatable shaft 22 being supported by the supporting windows 14A is rotatable within the supporting windows 14A and is movable within the supporting windows 14A vertically (or up and down) but is restricted from moving in the direction of the width W′ of the supporting window 14A.

The rotatable shaft 22 is provided thereon with an abrasive wheel (grinding element) 30, a pair of lateral coil springs 40 (40A and 40B) on either side of the abrasive wheel 30, and a pair of washers 50 each on the far end side of each coil spring 40 from the abrasive wheel 30.

The abrasive wheel 30 is provided at substantially the center of the rotatable shaft 22 in the axial direction. The abrasive wheel 30 is a cylindrical grinding element having a V-groove 32 in the circumferential surface, so that it has such a shape that a pair of truncated cone-shaped elements are connected to each other at the smaller diameter end surfaces so as to form the V-groove 32 in between or that a pair of oppositely beveled abrasive disks are connected to each other at the smaller diameter end surfaces.

On either side of the abrasive wheel 30, the lateral coil spring 40 is provided so that one end thereof is in touch with the abrasive wheel 30 and another end thereof is in touch with the washer 50 and so that each coil spring 40 is compressed by and between the abrasive wheel 30 and the washer 50. In other words, the abrasive wheel 30 is urged by the coil springs 40 towards the axial center of the rotatable shaft 22 as shown by A-1 and A-2 arrows in FIG. 4A so as to be at the center or at a middle point of the two vertical end walls 14 of the grinder casing body 10A. The two lateral coils springs 40 (40A, 40B) have the inner diameter slightly larger than the diameter of the rotatable shaft 22 so that they are loosely disposed around the rotatable shaft 22 on both sides of the abrasive wheel 30. Also, these coil springs 40 (40A, 40B) are substantially the same in length and have substantially the same spring force with each other. Thus, in FIG. 4A, the coil spring 40A urges the abrasive wheel 30 into the right direction shown by arrow A-1, and the coil spring 40B which is on another side of the abrasive wheel 30 urges the abrasive wheel 30 into the left direction shown by allow A-2 or in the opposite direction from the direction the coil spring 40A urges the abrasive wheel 30.

The washers 50 of a thin plate having an inner diameter slightly larger than the diameter of the rotatable shaft 22 are disposed on the rotatable shaft 22, and the outer diameter of the washers 50 is greater than the size of the supporting windows 14A, particularly greater than the width W′ (see FIG. 4B) of the supporting window 14A, of the end walls 14 of the grinder casing body 10A, so that the surface of each of the washers 50 that faces the end wall 14 is slidably in contact with the inner surface of the end wall 14.

The above described pair of grinder assemblies 10 each comprising the grinder casing body 10A, the horizontal rotatable shaft 22, the lateral coil springs 40 and the vertical coil springs 20 are installed in the grinding chamber so that they are respectively directly below the blade guide slits 5 formed in the cover casing 4 of the grinder casing body 10A and so that the rotatable shafts 22 and thus the grinding wheels 30 of these two grinder assemblies 10 are at bias or diagonal with respect to the length direction L′ of the blade guide slits 5 of the frame casing body 10A. More specifically, as seen from FIG. 2 and FIG. 5, in which the abrasive wheels 30 are drawn exaggeratingly for easier understanding, the pair of holding means 6 are provided on the bottom 3 a of the grinding chamber 3 so as to have a bias or diagonal angle of 10-25 degrees with respect to the length direction L of the grinding chamber 3, and thus the two grinder assemblies 10 that are respectively held by these holding means 6 each comprised of four projections 6 a are provided so that the center of the abrasive wheel 30 or the V-groove 32 thereof is at a bias or diagonal angle of about 10 to 20 degrees with respect to the length direction L′ of the blade guide slits 5 and the rotary shafts 22 take a symmetric positional relationship with each other about the center line C of the grinding chamber 3 which is at right angles to the direction of length L of the grinding chamber 3. However, the arrangement of the grinder assemblies 10 can take another manner in which the rotary shafts 22 are parallel to each other, and a only one (or single) grinder assembly 10 can be installed in a grinding chamber 3 of which cover casing 4 is formed only one blade guide slit 5 (or two blade guide slits 5).

In the above described structure, the abrasive wheel 30 has a cylindrical shape in which the V-groove 32 is in the axial center and in such a shape that a pair of two truncated cones (or beveled disks) of the same diameter are connected to each other at the smaller diameter end surfaces, thus having a symmetric grinding surfaces 32A and 32B along the V-groove 32, and thus being called in the description a “symmetric abrasive wheel.” This symmetric abrasive wheel is suitable to sharpen a double-edged blade X as shown in FIG. 11 that has the same blade surface XA and XB on both sides. The abrasive wheel in the present invention can be of another type as shown in FIG. 6. In this abrasive wheel 30′, the diameters of the two truncated cone elements (or beveled disks) are different from each other, so that the V-groove 32′ is asymmetric with one grinding surface 32A′ has more acute angle than the other grinding surface 32B′, thus being called in the description an “asymmetric abrasive wheel.” In the shown asymmetric abrasive wheel 30′, the grinding surface 32A′ on the left side is about 5 to 20 degrees with respect to the imaginary vertical line C′ and the grinding surface 32B′ on the right side is about 15 to 45 degrees with respect to the vertical center line C′. This asymmetric abrasive wheel 30′ is suitable to sharpen a single-edged blade Y as shown in FIG. 12 that has on one side of the blade a single blade surface YA (the blade Y can be formed with a minute blade surface YB on another side).

In use of the above-described blade sharpener, a pair of grinder assemblies 10 (more specifically, two grinder assemblies both having symmetric abrasive wheels, or both having asymmetric abrasive wheels or one having a symmetric abrasive wheel and the other having an asymmetric wheel) are set in the grinding chamber 3 by being held by the holding means 6, and the grinder assembly or assemblies 10 are filled with a liquid Lq, such as water or oil, and the grinding chamber 3 is covered by the cover casing 4.

With the cover casing 4 thus set and the grip 2 gripped by one hand, the blade (such as the blade X) of a knife held by another hand at the handle is inserted into the guide slit 5 and pressed down against the abrasive wheel 30 so that the cutting edge of the blade X comes into contact with the V-groove 32 of the abrasive wheel 30 and then moved back and forth inside the blade guide slit 5 along its length direction or in the direction of the width W of the grinding chamber 3. As a result, the blade surfaces XA and XB contact the grinding surfaces 30A and 30B while being pressed against thereto, and the blade X is thus sharpened. Since the blade X is pressed against the abrasive wheel 30, the rotatable shaft 22 is pressed and moved down within the supporting window 14A as shown in FIG. 7, and the longitudinal coil springs 20 press back (upward) the rotary shaft rotatable shaft 22 as indicated by upward arrows. The blade X thus receives pressing forces from above (by the user) and from below (by the longitudinal coil springs); and as a result, it is pressed substantially uniformly against the grinding surfaces 30A and 30B and thus sharpened evenly and efficiently.

In addition to these vertical pressing forces, the blade X receives lateral or horizontal pressing forces from one side (for instance, from the left side by the lateral coil spring 40A) and from another side (for instance, from the right side by the lateral coil spring 40B) when the blade X is moved back and forth in a reciprocating manner in the blade guide slit 5. More specifically, since the rotary shaft 22 is set to have a biased or diagonal angle relationship (of 10-20 degrees) with respect to the blade guide slit 5, when the blade X is moved in one direction, one lateral coil spring (for instance the spring 40A) is compressed and the other lateral coil spring (for instance spring 40B) expands, and when the blade X is moved in another or opposite direction, then the coil spring compressed (spring 40A) expands and the spring expanded (spring 40B) is compressed. When grinding is thus performed, these lateral or horizontal pressing forces that are opposite from each other in direction and are equal to each other in strength are repeatedly applied to the blade X. As a result, in addition to the vertical pressing forces by the user and longitudinal coil springs 20, the blade X repeatedly receives equal amount of lateral or side pressing forces from the two lateral springs 40 (40A, 40B) and is pressed sideways substantially uniformly and repeatedly against the grinding surfaces 30A and 30B of the abrasive wheel 30. The blade X is, accordingly, sharpened further evenly, efficiently and smoothly.

Also, during the back and forth movement of blade X with a pressing force applied thereto from above, the rotating abrasive wheel 30 can come in contact with the liquid Lq in the sharpening assembly 10. This liquid Lq absorbs the heat generated during the grinding and prevents the blade X from dulling that would be caused by heat, and it washes away grinding debris and thus maintains the grinding surfaces 30A and 30B in good grinding condition without getting clogged.

When the blade X is pressed against the abrasive wheel 30 as described above, the pressing back forces of the longitudinal coil springs 22 make the force of the abrasive wheel 30 applying to the blade X substantially uniform. As a result, with an addition of the lateral or horizontal pressing forces by the lateral coil springs 40, grinding of even a serrated edge knife such as bread slicing knives and fine ceramic blades and the like can be done efficiently.

A single-edged blade Y can be grinded in the substantially the same manner as in the blade X. The blade surface YA is brought into contact with the grinding surface 30A and blade Y is pressed down and moved back and forth within the guide slit 5, and the blade Y is sharpened while receiving the lateral forces from the lateral coil springs and also receiving the longitudinal forces from the longitudinal coil springs.

As seen from the above, according to the present invention, a blade to be sharpened (including both double-edged blade and single-edged blade) receives pressing forces of not only in the vertical direction (or in the up and down directions) but also in the horizontal direction (or in the right and left directions). Accordingly, the blade is grinded and sharpened smoothly and evenly, producing a sharp cutting edge.

In the above describe structure and operation, the grinder assembly 10 is provided with a pair of longitudinal coil springs and a pair of lateral coil springs. However, the object of the present invention can be accomplished by a structure that includes only a pair of lateral springs.

In this aspect of the present invention, as seen from FIGS. 8A and 8B, each one of pair of grinder assemblies 110 that are detachably installed in the grinding chamber 3 of the frame casing body 1 (they can thus be called grinder cassettes as well in view of the removability) comprises a grinder casing body 110A is formed by a rectangular bottom plate 102, a pair of end walls 104 vertically formed along the two end shorter side edges of the rectangular bottom plate 102 so as to face each other, and a pair of side walls 106 formed along two longer side edges of the rectangular bottom plate 102 to face each other. In each one of the pair (two) of end walls 104 facing each other, a supporting window 104A is opened.

In addition, the grinder assembly 110 further includes a rotatable shaft 122. This rotatable shaft 122 is provided within the grinder assembly 110 horizontally with its both ends inside the supporting windows 114A of the end walls 114. To the top surface of each one of the end walls 114 is attached a holding piece 104C so as to cover the upper opening of each of the supporting windows 114A and prevent the rotatable shaft 122 from being removed upwardly from the supporting windows 114A (or from the end walls 114 of the grinder assembly 110). The diameter of the rotatable shaft 122 is (slightly) smaller than the width W″ and height H″ of the supporting window 114A. As a result, the rotating shaft 122 is rotatable within the supporting windows 114A.

The rotatable shaft 122 is provided thereon with an abrasive wheel (grinding element) 130, a pair of lateral coil springs 140 (140A and 140B) on either side of the abrasive wheel 130, and a pair of washer 150 each on the far end side of each coil spring 140 from the abrasive wheel 130. This structure that includes the rotatable shaft 122 with the abrasive wheel 130, the lateral coil springs 140 and the washers 150 thereon and the functions of the these parts arc the same as those of the structure of the rotatable shaft 22 having thereon the abrasive wheel 30, the lateral coil springs 40 and the washers 50 shown in FIGS. 4A and 4B.

In addition, an asymmetric abrasive wheel 130′ as shown in FIG. 9 can be employed instead of the abrasive wheel 130 shown in FIG. 8. In this abrasive wheel 130′, the diameters of the two truncated cone elements (or beveled disks) are different from each other, so that the V-groove 132′ is asymmetric with one grinding surface 132A′ has more acute angle than the other grinding surface 132B′. In the shown asymmetric abrasive wheel 130′, the grinding surface 132A′ on the left side is about 5 to 20 degrees with respect to an imaginary vertical line C″ and the grinding surface 132B′ on the right side is about 15 to 45 degrees with respect to the imaginary vertical line C″. This asymmetric abrasive wheel 130′ is also suitable to sharpen a single-edged blade Y as shown in FIG. 12

The above described pair of grinder assemblies 110 each including the horizontal rotatable shaft 122 and the lateral coil springs 140 are installed in the grinding chamber 3 in the same manner as that of the grinder assemblies 10.

In use of the above-described blade sharpener, a pair of grinder assemblies 110 (in other words, two grinder assemblies both having symmetric abrasive wheel, or both having asymmetric, abrasive wheels or one having a symmetric abrasive wheel and the other having an asymmetric wheel) are set in the grinding chamber 3 by being held by the holding means 5. The grinder assemblies can be filled with a liquid Lq, such as water or oil, and the grinding chamber 3 is covered by the cover casing 4.

With the cover casing 4 thus set and the grip 2 gripped by one hand, the blade X of a knife held by another hand at the handle is inserted into the guide slit 5 and pressed down against the abrasive wheel 130 so that the cutting edge XE of the blade X comes into contact with V-groove 132 of the abrasive wheel 130 and then moved back and forth inside the blade guide slit 5 along its length direction or in the direction of the width W of the grinding chamber 3. As a result, the blade surfaces XA and XB contact the grinding surfaces 130A and 130B while being pressed against thereto, and the blade X is thus sharpened.

More specifically, the blade X receives lateral pressing forces from one side (for instance from the left side by the lateral coil spring 140A) and from another side (for instance from the right side by the lateral coil spring 140B) when the blade X is moved back and forth in a reciprocating manner in the blade guide slit 5. In other words, since the rotary shaft 122 is set to have a biased or diagonal angle relationship (of 10-20 degrees) with respect to the blade guide slit 5, when the blade X is moved in one direction, one lateral coil spring (for instance the spring 140A) is compressed and the other lateral coil spring (for instance spring 140B) expands, and when the blade X is moved in another or opposite direction, then the coil spring compressed (spring 140A) expands and the spring expanded (spring 140B) is compressed. When grinding is performed, these lateral or horizontal pressing forces that are opposite from each other in direction and are equal to each other in strength are repeatedly applied to the blade X. As a result, the blade X repeatedly receives equal amount of lateral or side pressing forces from the two lateral springs 140 (140A, 140B) and is pressed sideways substantially uniformly and repeatedly against the grinding surfaces 30A and 30B of the abrasive wheel 30. The blade X is thus sharpened evenly, efficiently and smoothly. The blade Y as shown in FIG. 12 can be grinded in the same manner as above with the grinder assembly shown in FIG. 9.

Thus, according to the above-described structure, since a blade to be sharpened (including both double-edged blade and single-edged blade) receives pressing forces in the horizontal direction (or in the right and left directions), the blade is grinded and sharpened smoothly and evenly, producing a sharp cutting edge.

Though the abrasive wheels 30 and 130 are formed by the same material entirely, the materials that make the grinding surface 30A and 130A can be alumina- or silicon-carbide ceramics, and the like, and the materials that make the grinding surfaces 30B and 130B can be different substances including silica clay ceramics, or alumina fine ceramics or alumina new ceramics, forming the surfaces smooth and hard.

In the above description, a pair of or two grinder assemblies are installed in the grinding chamber. However, only one or a single grinder assembly can be installed in the grinding chamber, and further, as seen from FIG. 10, the cover casing 4 can be formed with only one blade guide slit 5 so that a single grinder assembly 10 (110) is installed in the grinding chamber 3.

Also, though coil springs are described as an urging means to place the abrasive wheel to the center of the grinder assembly and to below the blade guide slit, any other replacement urging means can be used in the present invention such as a so-called washer-less-spring that is made of plastic. In addition, a permanent magnet and/or rubber sheets can be affixed to the underside of the frame casing body so as to prevent the sharpener from slipping during the use or grinding. 

1. A blade sharpener comprising: a frame casing body having a grinding chamber; and a grinder assembly detachably installed in the grinding chamber, said grinder assembly being comprised of: a grinder casing body having a pair of vertical walls facing each other, a supporting window provided in each of said pair of vertical walls, a rotary shaft provided between said pair of vertical walls with both end thereof in said supporting windows of said vertical walls, a grinding element provided on said rotary shaft at substantially an axial center thereof, and a pair of horizontally urging means each provided on either side of said grinding element.
 2. A blade sharpener comprising: a frame casing body having a grinding chamber; and a grinder assembly detachably installed in the grinding chamber, said grinder assembly being comprised of: a grinder casing body having a pair of vertical walls facing each other, a supporting window provided in each of said pair of vertical walls, a vertically urging means provided in each of said vertical walls, a rotary shaft provided between said pair of vertical walls with both end thereof in said supporting windows of said vertical walls and on said vertically urging means, a grinding element provided on said rotary shaft at substantially an axial center thereof, and a pair of horizontally urging means each provided on either side of said grinding element.
 3. The blade sharpener according to claim 1, wherein said grinding element is in substantially a cylindrical shape with a V-groove at an axial center thereof.
 4. The blade sharpener according to claim 2, wherein said grinding element is in substantially a cylindrical shape with a V-groove at an axial center thereof.
 5. The blade sharpener according to claim 1, wherein said grinding chamber is covered by a cover casing formed therein with a blade guide slit and said grinder assembly is disposed under said blade guide slit so that the rotary shaft of the grinder assembly is set to be at a biased angle with respect to a length direction of the blade guide slit.
 6. The blade sharpener according to claim 2, wherein said grinding chamber is covered by a cover casing formed therein with a blade guide slit and said grinder assembly is disposed under said blade guide slit so that the rotary shaft of the grinder assembly is set to be at a biased angle with respect to a length direction of the blade guide slit.
 7. The blade sharpener according to claim 3, wherein said grinding element is formed by a pair of beveled disks of different diameters so that smaller diameter sides of said pair of abrasive wheels of different diameters are connected to each other to form the V-groove.
 8. The blade sharpener according to claim 4, wherein said grinding element is formed by a pair of beveled disks of different diameters so that smaller diameter sides of said pair of abrasive wheels of different diameters are connected to each other to form the V-groove.
 9. The blade sharpener according to claim 1, wherein each of said horizontally urging means is a coil spring.
 10. The blade sharpener according to claim 2, wherein each of said horizontally urging means is a coil spring. 